CodeIgniter’s Image Manipulation class lets you perform the following
actions:

Image Resizing

Thumbnail Creation

Image Cropping

Image Rotating

Image Watermarking

All three major image libraries are supported: GD/GD2, NetPBM, and
ImageMagick

Note

Watermarking is only available using the GD/GD2 library. In
addition, even though other libraries are supported, GD is required in
order for the script to calculate the image properties. The image
processing, however, will be performed with the library you specify.

Regardless of the type of processing you would like to perform
(resizing, cropping, rotation, or watermarking), the general process is
identical. You will set some preferences corresponding to the action you
intend to perform, then call one of four available processing functions.
For example, to create an image thumbnail you’ll do this:

The above code tells the image_resize function to look for an image
called mypic.jpg located in the source_image folder, then create a
thumbnail that is 75 X 50 pixels using the GD2 image_library. Since the
maintain_ratio option is enabled, the thumb will be as close to the
target width and height as possible while preserving the original aspect
ratio. The thumbnail will be called mypic_thumb.jpg and located at
the same level as source_image.

Note

In order for the image class to be allowed to do any
processing, the folder containing the image files must have write
permissions.

Note

Image processing can require a considerable amount of server
memory for some operations. If you are experiencing out of memory errors
while processing images you may need to limit their maximum size, and/or
adjust PHP memory limits.

The preferences described below allow you to tailor the image processing
to suit your needs.

Note that not all preferences are available for every function. For
example, the x/y axis preferences are only available for image cropping.
Likewise, the width and height preferences have no effect on cropping.
The “availability” column indicates which functions support a given
preference.

Availability Legend:

R - Image Resizing

C - Image Cropping

X - Image Rotation

W - Image Watermarking

Preference

Default Value

Options

Description

Availability

image_library

GD2

GD, GD2, ImageMagick, NetPBM

Sets the image library to be used.

R, C, X, W

library_path

None

None

Sets the server path to your ImageMagick or NetPBM library. If you use
either of those libraries you must supply the path.

R, C, X
R, C, S, W

source_image

None

None

Sets the source image name/path. The path must be a relative or absolute
server path, not a URL.

dynamic_output

FALSE

TRUE/FALSE (boolean)

Determines whether the new image file should be written to disk or
generated dynamically. Note: If you choose the dynamic setting, only one
image can be shown at a time, and it can’t be positioned on the page. It
simply outputs the raw image dynamically to your browser, along with
image headers.

R, C, X, W

file_permissions

0644

(integer)

File system permissions to apply on the resulting image file,
writing it to the disk. WARNING: Use octal integer notation!

R, C, X, W

quality

90%

1 - 100%

Sets the quality of the image. The higher the quality the larger the
file size.

R, C, X, W

new_image

None

None

Sets the destination image name/path. You’ll use this preference when
creating an image copy. The path must be a relative or absolute server
path, not a URL.

R, C, X, W

width

None

None

Sets the width you would like the image set to.

R, C

height

None

None

Sets the height you would like the image set to.

R, C

create_thumb

FALSE

TRUE/FALSE (boolean)

Tells the image processing function to create a thumb.

R

thumb_marker

_thumb

None

Specifies the thumbnail indicator. It will be inserted just before the
file extension, so mypic.jpg would become mypic_thumb.jpg

R

maintain_ratio

TRUE

TRUE/FALSE (boolean)

Specifies whether to maintain the original aspect ratio when resizing or
use hard values.

R, C

master_dim

auto

auto, width, height

Specifies what to use as the master axis when resizing or creating
thumbs. For example, let’s say you want to resize an image to 100 X 75
pixels. If the source image size does not allow perfect resizing to
those dimensions, this setting determines which axis should be used as
the hard value. “auto” sets the axis automatically based on whether the
image is taller than wider, or vice versa.

R

rotation_angle

None

90, 180, 270, vrt, hor

Specifies the angle of rotation when rotating images. Note that PHP
rotates counter-clockwise, so a 90 degree rotation to the right must be
specified as 270.

X

x_axis

None

None

Sets the X coordinate in pixels for image cropping. For example, a
setting of 30 will crop an image 30 pixels from the left.

C

y_axis

None

None

Sets the Y coordinate in pixels for image cropping. For example, a
setting of 30 will crop an image 30 pixels from the top.

If you prefer not to set preferences using the above method, you can
instead put them into a config file. Simply create a new file called
image_lib.php, add the $config array in that file. Then save the file
in config/image_lib.php and it will be used automatically. You will
NOT need to use the $this->image_lib->initialize() method if you save
your preferences in a config file.

Text: The watermark message will be generated using text, either
with a True Type font that you specify, or using the native text
output that the GD library supports. If you use the True Type version
your GD installation must be compiled with True Type support (most
are, but not all).

Overlay: The watermark message will be generated by overlaying an
image (usually a transparent PNG or GIF) containing your watermark
over the source image.

Just as with the other methods (resizing, cropping, and rotating) the
general process for watermarking involves setting the preferences
corresponding to the action you intend to perform, then calling the
watermark function. Here is an example:

The above example will use a 16 pixel True Type font to create the text
“Copyright 2006 - John Doe”. The watermark will be positioned at the
bottom/center of the image, 20 pixels from the bottom of the image.

Note

In order for the image class to be allowed to do any
processing, the image file must have “write” file permissions
For example, 777.

This table shows the preferences that are available for both types of
watermarking (text or overlay)

Preference

Default Value

Options

Description

wm_type

text

text, overlay

Sets the type of watermarking that should be used.

source_image

None

None

Sets the source image name/path. The path must be a relative or absolute
server path, not a URL.

dynamic_output

FALSE

TRUE/FALSE (boolean)

Determines whether the new image file should be written to disk or
generated dynamically. Note: If you choose the dynamic setting, only one
image can be shown at a time, and it can’t be positioned on the page. It
simply outputs the raw image dynamically to your browser, along with
image headers.

quality

90%

1 - 100%

Sets the quality of the image. The higher the quality the larger the
file size.

wm_padding

None

A number

The amount of padding, set in pixels, that will be applied to the
watermark to set it away from the edge of your images.

wm_vrt_alignment

bottom

top, middle, bottom

Sets the vertical alignment for the watermark image.

wm_hor_alignment

center

left, center, right

Sets the horizontal alignment for the watermark image.

wm_hor_offset

None

None

You may specify a horizontal offset (in pixels) to apply to the
watermark position. The offset normally moves the watermark to the
right, except if you have your alignment set to “right” then your offset
value will move the watermark toward the left of the image.

wm_vrt_offset

None

None

You may specify a vertical offset (in pixels) to apply to the watermark
position. The offset normally moves the watermark down, except if you
have your alignment set to “bottom” then your offset value will move the
watermark toward the top of the image.

This table shows the preferences that are available for the text type of
watermarking.

Preference

Default Value

Options

Description

wm_text

None

None

The text you would like shown as the watermark. Typically this will be a
copyright notice.

wm_font_path

None

None

The server path to the True Type Font you would like to use. If you do
not use this option, the native GD font will be used.

wm_font_size

16

None

The size of the text. Note: If you are not using the True Type option
above, the number is set using a range of 1 - 5. Otherwise, you can use
any valid pixel size for the font you’re using.

wm_font_color

ffffff

None

The font color, specified in hex. Both the full 6-length (ie, 993300) and
the short three character abbreviated version (ie, fff) are supported.

wm_shadow_color

None

None

The color of the drop shadow, specified in hex. If you leave this blank
a drop shadow will not be used. Both the full 6-length (ie, 993300) and
the short three character abbreviated version (ie, fff) are supported.

wm_shadow_distance

3

None

The distance (in pixels) from the font that the drop shadow should
appear.

This table shows the preferences that are available for the overlay type
of watermarking.

Preference

Default Value

Options

Description

wm_overlay_path

None

None

The server path to the image you wish to use as your watermark. Required
only if you are using the overlay method.

wm_opacity

50

1 - 100

Image opacity. You may specify the opacity (i.e. transparency) of your
watermark image. This allows the watermark to be faint and not
completely obscure the details from the original image behind it. A 50%
opacity is typical.

wm_x_transp

4

A number

If your watermark image is a PNG or GIF image, you may specify a color
on the image to be “transparent”. This setting (along with the next)
will allow you to specify that color. This works by specifying the “X”
and “Y” coordinate pixel (measured from the upper left) within the image
that corresponds to a pixel representative of the color you want to be
transparent.

wm_y_transp

4

A number

Along with the previous setting, this allows you to specify the
coordinate to a pixel representative of the color you want to be
transparent.

Without a visual interface it is difficult to crop images, so this
method is not very useful unless you intend to build such an
interface. That’s exactly what we did using for the photo gallery module
in ExpressionEngine, the CMS we develop. We added a JavaScript UI that
lets the cropping area be selected.